Again, I don't mean remove the ability to edit it, I mean by default it copies the OP heading.
AFAIK, the subject heading does copy that of the OP when someone replies to it. Then one can change it if they want to. The subject heading above this reply now mirrors that of your original post without me editing it.
Is that what you mean or am I getting it wrong?
Read the title of my post. This is what he means.